New York [U.S.A], August 3: The United States has urged Americans currently in North Korea to leave the reclusive country before a travel ban policy takes effect on September 1.

That ban was announced last month and was published on Wednesday in the Federal Register.

The Trump administration will continue to permit four categories of travellers to visit North Korea after the policy takes effect, by applying for a special validation to their passport. Those categories are journalists, Red Cross officials, applicants whose travel is “justified by compelling humanitarian considerations,” and individuals whose visit is “otherwise in the national interest.”

The State Department announced the travel ban last month amid mounting concern over the safety of U.S. citizens visiting North Korea.

“Once in effect, US passports will be invalid for travel to, through and in North Korea, and individuals will be required to obtain a passport with a special validation in order to travel to or within North Korea,” State Department Spokeswoman Heather Nauert said in a statement.

In June, U.S. college student Otto Warmbier died following a prolonged detention in the country, provoking international outrage and calls for action in the Congress.

Warmbier had travelled to North Korea through a commercial tour company and was arrested for allegedly stealing a poster from his hotel.